Plasma processing apparatuses for thin film deposition, etching, and ashing have recently been used in the fabrication process of highly integrated semiconductor products. In particular, plasma processing apparatuses using microwaves or high frequency waves are frequently used because high density plasma can be stably generated even at a relatively low pressure (high vacuum state) of about 0.1 mTorr (13.3 mPa) to several 100 mTorr (several 10 Pa). Such plasma processing apparatuses are disclosed in Patent Documents 1 through 5 listed below.
A conventional plasma processing apparatus using microwaves will now be explained with reference to FIG. 1. FIG. 1 is a cross-sectional view of a conventional plasma processing apparatus 2 using microwaves. FIG. 2 is a cross-sectional view of an example of conventional holding stage structure in another plasma processing process.
Referring to FIG. 1, the conventional plasma processing apparatus 2 includes the holding stage structure 6 disposed in a process chamber 4 that can be vacuumed, and allowing a semiconductor wafer W (hereinafter referred to as a wafer W) to be placed thereon. The conventional holding stage structure 6 includes a supporting post 8 extending upright from the bottom of the process chamber 4, and a holding stage body 10 supported on an upper end of the supporting post 8. The wafer W is placed on a top surface of the holding stage body 10. A resistance heater 12, a heating unit, is buried in the holding stage body 10, and an electrostatic chuck 14 for holding the wafer W using an electrostatic force is formed near the top surface of the holding stage body 10.
A guide ring 15 having a quasi-L-shaped cross-section is attached around the periphery of the top surface of the holding stage body 10 on which the wafer W is placed. The inner diameter of the guide ring 15 is slightly greater than the outer diameter of the wafer W, so that the wafer W is prevented from laterally sliding and from being displaced from a proper position. A top plate 16 is hermetically installed on the process chamber 4 to face this holding stage structure 6. The top plate 16 has a disk shape and is formed of aluminum nitride or quartz through which microwaves pass. Also, a gas nozzle 18, which is a gas introducing unit for introducing a predetermined gas into the process chamber 4, is formed in a sidewall of the process chamber 4.
A planar antenna member 18 that is disk-shaped and has a thickness of several millimeters (mm), and a wavelength-shortening member 20 formed of, for example, a dielectric material are installed on a top surface of the top plate 16. The wavelength-shortening member 20 is used to shorten the wavelength of microwaves in a radial direction of the planar antenna member 18. A plurality of slots 22, which are through-holes having narrow and long shape, are formed in the planar antenna member 18. An inner conductor 26 of a coaxial waveguide 24 is connected to the center of the planar antenna member 18. Accordingly, microwaves of, for example, 2.45 GHz generated by a microwave generator 28 are converted into a vibration mode by a mode converter 30, and then guided to the planar antenna member 18. The microwaves guided to the planar antenna member 18 are propagated in the radial direction of the planar antenna member 18, radiated through the slots 22 of the planar antenna member 18, passed through the top plate 16, and introduced into the process chamber 4. Plasma is generated in a processing space S of the process chamber 4 due to the microwaves, and a predetermined plasma process, such as etching or thin film forming, is performed on the wafer W.
The conventional holding stage structure of FIG. 2 may include, instead of the guide ring 15, a circular receiving recession 32 having a diameter which is slightly greater than the diameter of the wafer W, and formed in the center of the top surface of the holding stage body 10 on which the wafer W is placed. The position of the wafer W is determined by a sidewall 34 of the receiving recession 32.
[Patent Document 1] Japanese Laid-Open Patent Publication No. hei 3-191073
[Patent Document 2] Japanese Laid-Open Patent Publication No. hei 5-343334
[Patent Document 3] Japanese Laid-Open Patent Publication No. hei 9-181052
[Patent Document 4] Japanese Laid-Open Patent Publication No. 2003-332326
[Patent Document 5] Japanese Laid-Open Patent Publication No. 2005-142529